Streamlined rings for assuring isentropic compression of supersionic stream through a conventional missile diffuser



March 21, 1961 R. s. RAE 2,975,587 ASSURING ISENTROPIC COMPRES SION STREAMLINED RINGS FOR OF SUPERSONIC STREAM THROUGH A CONVENTIONAL MISSILE DIFFUSER Filed Nov. 16, 1949 FIG! INVENTOR.

RANDOLPH S. RAE

ATTORNEY Un te S e aw-Q...

Randolph S. Rae, Silver Spring, Md., assignor to the United States of America as represented by the Secretary of the Navy Filed Nov. 16, 1949, Ser. No. 127,127

6 Claims. '(Cl. till-35.6)

The present invention relates to guided missiles. More specifically, it relates to air intakes from ram jets.

The supersonic ram jet inlets now in use, such as the Oswatitsch diffuser, the multiple shock diffuser and the wing scoop diffuser, create generally two main problems. Primarily, the full isentropic compression of the supersonic stream entering the diffuser duct is not attainable in the above mentioned dilfusers, since the angle of the lip of the cowling is greater than the maximum permissible angle possible, for assuring attachment of the shock wave to said lip in the outer stream. This excessive lip angle results in a curved shock wave which interferes with the flow within the duct, resulting in nonisentropic compression. A further objection to said above portioned diffusers is one relating to the retarding force on the unit, or aerodynamic drag, produced when the missile is traveling at supersonic speeds.

An object of the present invention, therefore, is to provide a ram jet diffuser intake having a compression of the supersonic stream, approaching isentropic values.

Another object of the present" invention is to provide a ram jet diffuser intake having a minimum amount of aerodynamic drag but nevertheless providing full utilization of supersonic compression.

Other objects any many of the attendant advantages of the invention will be readily appreciated as the same becomes understood by reference to the following detailed description, when considered in connection with the accompanying drawings, wherein:

Fig. 1 is a diagrammatic axial section through the forward end of a ram jet provided with a modified swatitsch diffuser embodying the invention, the center body being shown in. elevation;

Fig. 2 is a section through the same in the plane 22 of Fig. 1;

Fig. 3 is a diagrammatic axial section through the forward end of a ram jet provided with a modified fonn of multiple-shock diffuser that embodies the present invention, the center body being shown in elevation;

Fig. 4 is the corresponding front end view;

r Fig. 5 is a diagrammatic perspective view, partly in section illustrating a wing scoop diffuser applied to a wing of a supersonic aerial vehicle, modified to include the present invention; and

Fig. 6 is a diagrammatic section illustrating a multipleshock, wing scoop diffuser, embodying the present invention.

Referring to the drawing and particularly to Figs. 1 and 2 there is shown a compression nozzle or diffuser section 1 of the body of a ram jet 2. The diffuser consists in general of a compression shroud in the form of a cylindrical cowling 3, and an axially located symmetrical center body 4. Suitable struts 5 are provided to hold, and aline, said center body in a fixed relationship to the ram jet cowling 3, with the vertex 7 of the center body 4 extending substantially in front of the lip 6 thereof. The structure so far described is substantially the Oswatitsch diffuser which is well known in the art.

Patented Mar. 21, 1961 ICC To overcome the aforesaid objections to the Oswatitsch diffuser, it is necessary in accordance with the present invention to secure in front of the diffuser 1 an auxiliary shroud in the form of an annular streamlined body 10. The inner surface 11 of the body 10 is cylindrically shaped and coaxial with the ram jet diffuser. The body 10 may be provided with struts 12 which aline and secure said body in a fixed relationship with respect to the center body 4. The leading edge 13 of the body 10 extends materially in front of the vertex 7 of the center body 4 and the aft end 14 blends with the general contour of the cowling 3, and overlaps a portion of the cowling lip 6. The angle of the outer surface 15 of the body 10 may be varied by merely increasing or decreasing the overall length of said body. A curved surface 16 is provided at the rear end of the body 10 and is substantially concentric with the contour of the lip 6 of the cowling 3. A slot 17, between the surface 16 and the lip 6, is provided to insure stability of the diffuser when the latter is subjected to pressure fluctuations during flight.

Referring now to Figs. 3 and 4, there is shown a ram jet multi-shock diffuser 20 consisting of elements as described hereinabove for Figs. 1 and 2. A difference exists mainly in the contour of the inner body 21 and 22, which at its leading end consists of a cone C followed by a frustum F of another cone. A streamlined body 23, similar in detail to the body 10 shown in Fig. l is provided in front of said difiuser 20.

In Fig. 5 is shown a wing scoop diffuser 25 with a forwardly extending baffie or streamlined body 26 cooperating therewith. This scoop diffuser is illustrated as mounted on a wing W of a ram jet. The lip 6a corresponds to the lip 6 of the previously described forms, however said lip 6a is not a surface of revolution but is curved only in one direction, that is, it is a ruled sur-. face of cylindrical nature. Similar remarks apply to the curved surfaces of elements 4a, 7a and 1611.

In Fig. 6 there is shown a multiple-shock wing scoop diffuser 30 with the streamlined body 31 cooperating therewith and protruding forwardly therefrom. Here again reference characters 6a, 16a, 21a and 22a correspond to 6, 16, 2.1 and 22 respectively, of Fig. 3, but represent singly-curved surfaces. It will be noted that the cone C and conic frustum F of Fig. 3 are replaced by plane surfaces C and F in Fig. 6.

It will be understood that whereas the two examples illustrated in Figs. 1 to 4 inclusive are shaped as solids of revolution about the axis of the center body in each, the forms of the invention illustrated in Figs. 5 and 6 are not solids of revolution but are of unvarying cross sections in planes parallel to the plane of these figures throughout their entire widths, as follows from their singly-curved surfaces. Whereas the Figs. 1 to 4 forms are designed for the entrance end of ram jets, the Figs. 5 and 6 forms may be placed anywhere along the body portion of the ram jet, or other supersonic vehicle, preferably on the wings thereof, to collect air from the surrounding atmosphere and feed it into the ram jet or the like.

The embodiments of Figs. 5 and 6 will usually be applied to some existing lateral extension of the ram jet, for example, a wing or vane. These are usually double walled structures, for strength and lightness, and thus constitute ready-made conduits that may be used to convey the air from the scoop to the interior of the ram jet.

It is obvious that, when associated with the forwardly extending streamlined body hereinabove described, the angle of the cowling lip is no longer limited by aerodynamic flow considerations. This fact insures the full utilization of maximum supersonic compression possible and also insures that the heretofore objectionable aerodynamic drag resulting from a steep lip angle necessary 3 for such compression is obviated by the externally-{aired contour of said streamlined body.

The improvement in pressure recovery efficiency attained by means of the present invention, over the prior art devices increases with the Mach number-and becomes very considerable athigh'supersonic speeds.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. A ram jet diffuser, comprising an air entrance tube having a contraction at its forward end, a center body placed axially of said tube and tapering to a point at each end, one of said tapered ends extending partly out of the forward end of said'tube, said endjhaving a conical surface, followed by a frusto-conical surface having a greater slope with respect to the axis of the center body, i'nrturn followed by a smoothly curved surface of revolution' extending to the other end of the center body, and an annular sleeve coaxial with said tube, extending forward beyond the forward end of said center body and rearward beyond the forward end of said tube.

2. A ram jet diffuser, comprising an air entrance tube having a contraction at its forward end, a center body placed axially of said tube and tapering to 'a point at each end, one of said tapered ends extending partly out of the forward endof said tube, said center body being bounded by a surface 'of revolution extending throughout the length of the center body, and an annulansleeve coaxial with said tube, extending forward beyond the forward end of said center body and rearward beyond the forward end of said tube, said sleeve having a cylindrical bore at its forward end.

3. A ram jet diffuser, comprising an air entrance tube having a contraction at its forward end, a center body placed axially of said tube and tapering to a point at each end, one of said tapered ends extending partly out of the forward end of said tube, said end having a conical surface, followed by a frusto-conical surface having a greater slope with respect to the axis of the center body, in turn followed by a smoothly curved surface of revolution extending to the other end of the center body, and an annular sleeve coaxial with said tube, extending forward beyond the forward end of said center body and rearward beyond the forward end of said tube, said sleeve having a cylindrical bore at its forward end, coextensive rearwardly with the baseof said conical surface.

4. A diffuser for a ramjet engine comprising a cowling defining an entrance for the admission of the gases through which the engine travels, a body within said cowling and coacting with said cowling to provide passage for the gases entering said cowling, said body having a surface adapted for deflecting the gases through which the engine travels at increasing an'gularityto the direction of travel of the engine, said body extending forwardly and aft of said entrance, and a streamlining member supported adjacent said entrance and in spaced relationship thereto, said member projecting forwardly of said body, and aft beyond the entrance defined by said cowling.

5. A diifuser as recited in claim 4 wherein said entrance is substantially annular in cross section.

6. A diffuser as recited in claim 4 wherein said e'n-' trance is substantially rectilinear in cross section.

References Cited in the file of this patent UNITED STATES PATENTS 2,540,594 Price Feb. 6, 1951 2,612,749 Tenney et al Oct. 7, 1952 2,631,425 Nordfors Mar. 17, 1953 FOREIGN PATENTS 614,548 Great Britain Dec. 17, 1948 

